The structural components of vehicles, such as aircraft, are comprised of increasing amounts of composite materials, such as carbon fiber reinforced plastic (CFRP). Heat damage to such composite materials may occur from a number of causes, including a lightning strike, an electrical short in wiring, or an overheated component. When heated to an elevated temperature for an extended period of time, composite materials may lose some of their desirable mechanical properties. In particular, such heating may reduce the ability of the composite materials to withstand mechanical stresses.
Currently, non-destructive testing of composite materials is performed with a portable FTIR (Fourier Transform Infrared) spectrometer to identify any potential degradation. An FTIR spectrometer uses the selective IR (infrared) absorbance of different chemical compounds, so that oxidized carbon is easily distinguished from unoxidized material. The relatively grainy consistency of the composite material leads to results that may be highly variable on a scale of the inspection area, which typically is 1 mm in diameter. This requires measurements to be made on a statistically significant number of different nearby spots in order to reach a reliable conclusion on the degree of damage.
Such FTIR spectrometers are relatively large and expensive. Further, their size does not lend their use to inspection of composite materials in difficult-to-reach areas. Accordingly, there is a need for a small, portable, and inexpensive system for measuring thermal degradation of composites.